0 for Cpx assays) at 37°C. Overnight cultures were diluted to an OD600 of 0.005 into fresh media and grown with shaking in a gyratory water bath at 37°C. Duplicate samples (0.5 ml) were taken throughout the early exponential phase www.selleckchem.com/products/BAY-73-4506.html of the growth curve (OD600 = 0.08-0.4) and β-galactosidase activity was measured by the standard assay [53]. EσE and Cpx activities shown in Figure 1 were determined from the slope on the line of a differential plot of β-galactosidase activity in 0.5 ml of culture versus OD600 and normalized to the wild-type case. In Figure 3, the average β-galactosidase activity/OD600 (Miller Units) was calculated and normalized to that of wild-type. Statistical

analysis was performed using a Student’s t-test. Western blot analysis Whole cell extracts were prepared by resuspending cells in urea protein sample buffer (8 M urea, 200 mM Tris-Base, 200 mM DTT, 2% SDS, 0.02% bromphenol blue) followed by short sonication and heating of the sample to 95°C for 10 min. Extracts from equal numbers of cells were run on SDS-polyacrylamide gels and transferred to nitrocellulose membranes. The membranes were probed with dilutions of rabbit polyclonal antisera raised against SurA (1:10 000), PpiD (1:10 000), DegP (1:20 000), Hsc66 (1:20 000), LamB (1:3000), and with mouse

monoclonal antibodies raised against OmpA (1:500), respectively. Alkaline phosphatase conjugated goat anti-rabbit selleck chemical and anti-mouse IgGs (Sigma, 1.10 000 dilutions), respectively, served as secondary antibodies. They were visualized by incubating L-NAME HCl the blots in reaction buffer (100 mM Tris-HCl, pH 8.8, 100 mM NaCl, 5 mM MgCl2, 37.5 μg/ml nitro blue tetrazolium, 150 μg/ml 5-bromo-4-chloro-3-indolyl phosphate). Signal intensities were quantified using ImageJ software http://​rsb.​info.​nih.​gov/​ij/​. Hsc66 and MalE were used as the internal standard for each lane. Experiments

were repeated a minimum of two times for each strain and condition, and data for one representative experiment are shown. Preparation of OmpA folding intermediates During the course of SurA depletion, samples corresponding to an equal number of cells were harvested by Selleck Ruxolitinib centrifugation and immediately frozen in a dry ice/ethanol bath. Folded and unfolded OmpA folding intermediates were isolated by gentle lysis as previously described [33]. Samples were mixed with protein sample buffer (3% SDS, 10% glycerol, 5% β-mercaptoethanol in 70 mM Tris, HCl, pH 6.8), heated to 37°C for 10 min and loaded onto 12.5% SDS-polyacrylamide gels. Electrophoresis was performed at 50 V and OmpA intermediates were detected by Western blot analysis as described above. Protein purification N-terminally His6-tagged PpiD proteins and C-terminally His6-tagged SurA were produced in E. coli CAG44102 from pASKssPpiD, pASKssPpiDΔParv and pASKSurA, respectively, and purified from the periplasmic fraction by affinity chromatography on Ni2+-chelating sepharose as previously described [2].